1. Technical Field
The present invention is related to an analog modem system, and more particularly, to an analog modem system in which a second logical channel is used to transmit certain diagnostic data.
2. Background Information
In a typical analog modem system, illustrated in FIG. 1, one modem 102 connects to another modem 104 via telephone lines 106 to transmit and receive information. In order for the modems to communicate with each other, each modem must first determine what type of modem with which it is attempting to communicate, in order to, inter alia, transmit data at the correct rate, using an optimum protocol.
For a number of reasons, it may be desirable to enable one modem device to identify itself to another modem device during the modem initialization process such that, if the devices are compatible with each other, a number of enhanced features can be prompted or employed. The use of such differentiated features may allow certain compatible modem devices to operate in an improved manner, relative to incompatible modem devices. However, the standard handshake sequences used by two modem devices (typically client and central site modems, although the invention may be used in the context to two client modems or two central site modems) to establish communications have only a limited capability to exchange manufacturer-specific information for system identification, configuration, and diagnostics.
The conventional V.8bis handshake sequence provides some capability to exchange system-specific information during the initial handshake procedure. For instance, some modem manufacturers use this V.8bis handshake sequence to exchange limited diagnostic and identification information. This exchange is only available at the beginning of a call, however, as manufacturers generally do not wish to prolong the handshake sequence. Using the handshake sequence to exchange diagnostic and identification information is generally undesirable, as the user would be sitting and waiting longer for the connection to be established. During the handshake sequence, data is being transmitted at a relatively low rate until the modems determine the type of modem with which it is communicating, they cannot transmit at their maximum speed. Therefore, it is not desirable to transmit a large amount of data before the handshaking sequence is completed and a data channel is opened.
The manner in which the modem devices exchange the identification data and the type of data exchanged can be varied to address a number of practical issues, e.g., improved performance at a central site ISP location, improved diagnostic information available to the central site ISP location, as well as differentiated features that may be developed in the future. The performance associated with a central site may be related to the number of unintentional call disconnections, the number of calls that progress beyond the initial handshaking procedure, the data rates obtained during the connections, and other functional aspects of the modem connections established through the central site.
During the handshaking procedure, it may be desirable to exchange as much information as possible for diagnostic and identification reasons. Such an exchange should consider the duration of the handshake sequence: it is typically undesirable to significantly lengthen the duration of the handshake sequence. Furthermore, the transmission of diagnostic data and identification information should be transparent to the user. In addition, it is desirable to identify the client modem very early in the handshake sequence so that the central site modem can capture the information and utilize it to help diagnose and address connectivity problems in the field. It is thus desirable for a modem to have a short handshake period along with full-featured end-to-end diagnostics. It would be desirable to enhance the ability of the two modem devices to exchange such information, without burdening the initial handshake and thereby delaying the time needed to establish a connection. In addition, it would be desirable to establish the presence of a communications channel between the two modem devices that is available throughout the call, not just at the beginning of the call.
One method for satisfying some of those needs is the installation of a higher-level application program, e.g., an SNMP-based or an HTTP-based application, that can be used for the exchange of diagnostics, configuration, and the like. However, these types of programs tend to be costly, and, as such, they are not yet widely deployed.